ABSTRACT
The most important groups of inorganic ion exchangers are clays, zeolites, hydrous oxides, insoluble acid salts, heteropolyacids, and hexacyanoferrates. Some of these inorganic ion exchangers exhibit especially high selectivities for certain elements or groups of elements. This chapter examines representative examples of the selectivities of inorganic exchangers for comparison with those of organic ion-exchange resins. The inorganic ion exchangers, unlike their organic analogs, usually have rigid structures and do not undergo any appreciable dimensional change during the ion-exchange reaction. The chapter discusses the selectivity of inorganic ion exchangers in terms of an ion sieve effect, steric factors, ion size preference, an entropy effect and ion memory preference.
